Fixes  #99

Refactor input generation code from the view to low level translation such that
current export in question during post and delete is handled cleanly.
Add no_root_squash option temporarily as a stop gap till user mapping code
is figured out.
Bugfix: When a share with no nfs exports exists, nfs export of other shares
resuults in error.

When creating input for low level nfs export code, don't create empty
dictionary(default) for shares with no nfs exports.
Merge pull request #109 from schakrava/issue#99_nfs_export_input

Fixes  #99